Nowadays nano-sized Spin CrossOver (SCO) particles receive more and more interests not only for the exploration of the physical properties of these materials at the mesoscopic scale, but also for the development of new functional materials. Up to now observations of the spin transition property was essentially reduced to the simple investigation of temperature dependence of the magnetization or the optical absorption in a huge ensemble of nano-particles with different degrees of size and shape dispersion. The development of methods for single Spin CrossOver (SCO) particle measurements is desirable for both fundamental and applicative perspective even if such efforts remain scare so far.
In the field of nano-scale magnetic measurements, the state of the art is represented by the micro-SQUID and nano-SQUID devices. These devices can detect the magnetization reversal of small amount of magnetic nano-particles or single molecule magnets by depositing directly the nano-particles on the micro-bridge Josephson junctions.
However, for low noise operation, the micro-bridges are normally made of low temperature superconducting materials such as niobium. Such devices are for example described in the article entitled “Magnetic Anisotropy of a Single Cobalt Nanocluster” from M. Jamet and al., published in the Physical Review Letters, Vol. 86, number 20.
Hitherto the working temperature of such a magnetometry detection system is limited below few tens of Kelvin.
Consequently, the conventional micro-SQUID technique is not appropriate to study the magnetization properties within the room temperature range, especially to carry out precise measurements of room temperatures switching properties of a small volume or a single nano-particle of a SCO material.
The current ultra-sensitive SQUID detection method suffers from several drawbacks as being used at very low temperature and requiring complex instruments that are not portable and not flexible.
Alternative methods are proposed as described in the following documents:                the article from Sunjong Oh et al. untitled “Analytes kinetics in lateral flow membrane analyzed by cTnl monitoring using magnetic method”, published in Sensors and Actuators B: Chemical International devoted to Research and Development of Physical and Chemical Transducers, Elsevier S. A., Switzerland, vol. 160, n °1, 19 Aug. 2011, pages 747-752;        the article from Sunjong Oh et al. untitled “Hybrid AMR/PHR ring sensor”, published in Solid State Communications, Pergamon, GB, vol. 151, n °18, 29 May 2011, pages 1248-1251;        the patent application US 2006/194327 A1;        the patent application US 2010/231213 A1.        
A technical problem is to avoid such disadvantages and to provide an ultra-sensitive magnetometry system that performs measurements at room temperature, which is less complex and offers a more portable and flexible implementation
In addition, another technical problem is to propose a magnetometry system and method that improves the sensitivity detection performance in order to detect nano or picotesla field generated by a “single micro/nano object” in the close vicinity of the sensor active surface.